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'UNITED STATES PATENT OFFICE.

GEORGE M. GITHENS, OF BROOKLYN,` NEW YORK.

STEAM ROCK-DRILL.

SPECIFICATION forming part of Letters Patent No. 25'7,938, dated May 16, 1882. Application filed September 30,1881. (No model.)

To all zrhom it may conce'n u Be it known that I, GEORGE M. GITHENS, of Brooklyn, E. D., in the county of Kings and State of New York, have invented an Im provement in Steam Rock-Drills, of which the following isa specification.

Rock-drills are usually made with a cylinder containing a pisten, the rod of which is connected with the rock-drill. The heads of the cylinder have been bolted together by bolts running through both heads. When the drill is in use the piston sometimes strikesupon the forward head in consequence of the drill entering a seam in the rock, or passing into a soft portion of such rock, and the bolts are often broken. A cushioning device has been used to lessen the concussion; but this does not relieve thebolts from the concussion,which appears to granulate or crystallizc the metal, and cause the same' to break.

My present invention is made for inpartiug elasticity to the bolts themselves, so that they will'yield when the piston strikes against the inside of the head, and prevent iujury to the parts. e p i In the drawings, Figure 1 is a vertical section of the cylinder, and Fig. 2 is au elev'ation of one of the bolts and its nuts, and section of the cross-bar. i

The piston a, piston-rod b, and cylinder c are of the usual character employed with rockdrills, and the heads d 'and e are also of ordinary Construction, except that the back head is made convex in the center, as at f. The heads d and e have holes through them for the passage of the bolts IL, and the nuts i are applied at the ends of the bolts; but said bolts, instead of being straight, are zigzag in compound curved liues, as seen in Fig. 2, so that said bolts are longer than they otherwise would be, and the extra'legth is taken up in the bends, and hence such bolts become springs that are verytrigid, and do not yield to the pressure of steam, or' the ordinary conditions of use 5 but in case the piston strikes against the inner surface of the head d, the bolts will yield instead of becoming injured. As an ad ditional protection against injury, I apply a cross-bar, I, with eyes or forks at its ends for the bolts to pass through, such cross-bar resting upon the convexity or central hearing of the back head, and the nuts of the rods coming up against this bar at its ends, so that said bar becomes a very stifi' leverspring that bends slightly under severe concussion. This bar is preferably of wrought iron or steel, and the risk of injury to the parts by concussion is lessened by the yieldin g character of the bar.

The bolts h having the compound curved bends may pass from one head to the other, or there may be separate bolts for the respective heads. lu this latter case there will be lugs near the middle of the cylinder for the respectivc bolts.

lt' the cross-bar l should receive a set or bend in one direction, it may be turned over so that the tendency will be to bend the same in the other direction. This bar may be of metal or of Wood, or of metal and wood in layers.

I claim as my invention i 1. The conhination, with the piston, cylin-- same, and bolts passing through the ends of So the cross-bar, for the purposes and substantially as set forth.

3. The combination, with thecylinder and piston in a rock-drill, of a head having a een tral hearing, a cross-bar, bolts having the bodies bent into curved liues, and nuts, substantially as set forth.

Signed by me this 2Tthday of September, A. D. 1881.

GEO. M. 'GETE ENS.

Witnesses GEO. T. PINCKNEY, WILLIAM G. MOTT. 

